Safety device for electrical apparatus



June 19, 1928.

H. MICHULITZ SAFETY DEVICE FOR ELECTRICAL APPARATUS Filed Feb. 10, 1927 Inventor: Hermann Michulitz,

His Attorney Patented June 19, 1928.

UNITED STATES PATENT OFFICE.

HERMANN MICHULITZ, F BERLIN, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COM- IPANY, A CORPORATION OF NEW YORK.

SAFETY DEVICE FOR ELECTRICAL APPARATUS.

Application filed February 10, 1927, Serial No. 167.343, and in Germany March 2, 1926.

My invention relates to safety devices for encased oil immersed electrical apparatus such as transformers, reactors and the like. Safety devices for oil immersed electrical apparatus have been proposed in which the gases developed the result of a defect in the apparatus are collected and used to actuate an alarm or disconnecting device. Some gas is often given off, however, during normal operation of the apparatus and although the rate at which the gas is given off in this way may be very small, yet a sufficient quantity may finally collect to cause the safety device to be actuated when this is not desired. The object of the invention is to pro vide an improved safety arrangement which may operate without this undesirable result.

The invention provides a receptacle or enclosure for the collection of the gas, the receptacle having an opening which is normally closed but which is opened automatically to permit the gas to escape when the level of a body of oil in the receptacle falls. The opening should be of such size that the rate at which the gas can escape will be less than that at which it will collect as the result of a trouble in the apparatus so that when trouble does occur a sufficient quantity of gas may collect to actuate the safety de vice.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Fig. 1 is a detail sectional view of one form of the invention and Fig. 2 shows how the invention may be applied in connection with an oil-immersed transformer.

Like reference characters indicate similar parts in both figures of the drawing.

In the form of the invention shown in the drawing, a receptacle communicates with the pipe 11 leading from the transformer casing 12 to a conservator or expansion chamber 13, the receptacle 10 being normally full or nearly full of oil. The cover 14 of the receptacle 10 has an outlet which may be closed by a valve 15. The valve 15 is connected to a float 16 which. when the oil level vis sufficiently high, presses the valve against its seat to close the outlet in the cover 14. The downward or opening movement of the valve is limited by a stop 17 connected to the valve and resting on a cap 18 threaded onto a support 19 above the outlet in the cover 14. The cap 18 has openings for the escape of gas. The maximum opening of the valve may be easily adjusted and controlled by turning the cap 18 which supports the valve to regulate the rate at which gas may escape. Thus the opening past the valve may be restricted as desired.

The receptacle 10 normally contains suflicient oil to keep the valve 15 closed but when gas collects in the receptacle, the level of the oil and the float 16 will drop and the valve 15 will open to permit the gas to escape. Now, if gas continues to accumulate more slowly than it can escape through the valve or if it ceases to accumulate, then the oil level can drop only a small distance and the valve may finally close again. If, however, there is some trouble which causes gas to accumulate more rapidly than it can escape through the valve, then the oil level will continue to drop until finally a main normally immersed float 20 will fall to close a pair of contacts 21. The contacts 21 control a safety circuit which may include a signal 22 or other safety device. Thus, the safety device will operate in response to the evolution of gas at a. substantial rate, such as may be due to trouble of any consequence but the device will not operate when such trouble is nonexistent or insignificant.

The invention has been described in what is now considered its preferred form but it will be obvious that changes may be made without departing from the scope of the invention as defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A safety device for encased, oil-immersed electrical apparatus, said device including a receptacle containing oil and arranged to receive gas from the casing of said apparatus, said receptacle having an outlet for the escape of said gas. safety circuit controlling means responsive to a predetermined drop in the oil level in said receptacle, and means responsive to a smaller drop in said oil level to open and close said outlet.

2. A safety device for encased oil-imtit) mersed electrical apparatus, said device including a receptacle containing oil and arranged to receive gas from the casing of said apparatus, said receptacle having an outlet 5 for the escape of said gas, safety circuiteontrolling means responsive to a predetermined drop in the oil level in said receptacle,

means responsive to a smaller drop in said oil level to open and close said outlet, and means for limiting the maximum opening 0 of said outlet.

In Witness whereof, I have hereunto set my hand this 27th day of January. 1927.

HERMA NN MICI-[UI II'TZ. 

